OBD-II Trouble Code Technical Description
Ambient Air Temperature Sensor Performance
What does that mean?
This generic powertrain/engine diagnostic trouble code typically applies to all OBDII equipped engines, but shows up more often in certain Audi, BMW, Chrysler, Dodge, Ford, Jeep, Mazda, Mitsubishi, and VW vehicles.
The Ambient Air Temperature (AAT) sensor converts ambient air temperature into an electrical signal for the Powertrain Control Module (PCM). This input is used to modify air conditioning system operation and display outside air temperature.
The PCM receives this input and possibly two more; Intake Air Temperature (IAT) and Engine Coolant Temperature Sensor (ECT). The PCM looks at the AAT sensor voltage and compares it to the IAT/ECT sensor readings when the ignition switch is first turned on after a long cool down period.